Conventionally, cotton which is a natural fiber, and an organic fiber are used as a cut-resistant raw material, and woven/knitted textiles into which such a fiber and the like are knitted are widespread in fields in which cut resistance is required.
Knitted products and woven products have been suggested which are produced by using spun yarns of a high strength fiber such as an aramid fiber so as to provide cut resistance. However, the knitted products and woven products have been unsatisfactory from the standpoint of fiber detachment and durability. On the other hand, another method in which cut resistance is enhanced by using a metal fiber together with an organic fiber or a natural fiber is attempted. However, the use of a metal fiber not only causes texture to become hard, thereby deteriorating flexibility, but also causes product weight to become heavy, thereby become difficult to handle.
As an invention for solving the aforementioned problems, a polyethylene fiber having a high elastic modulus has been suggested which is produced by a so-called gel spinning method using a solution in which a polyethylene is dissolved in a solvent (for example, see Patent Literature 1). However, the elastic modulus of the polyethylene fiber is excessively high, so that a problem arises that the fiber has a texture representing an increased hardness. Further, a problem arises that the use of the solvent causes deterioration of a working environment for producing the polyethylene fiber. Further, a problem arises that the solvent which remains contained in the polyethylene fiber obtained as products causes an environmental load in indoor and outdoor applications even in a case where the solvent which remains contained therein is slight.
Further, the specifications are diversified in fields in which the cut-resistance is required, and various applications are considered. For example, some of cut-resistant gloves may be produced by a heat treatment process being performed during a resin treatment for prevention of slipping, whereas knitted fabrics which are not subjected to the resin treatment may be used as they are. In this case, in a temperature range (about 20° C. to 40° C.) in actual use, a dimensional stability is required, and a shrinkage stress and a shrinkage rate are preferably low. Furthermore, as another application, an application as protective covers for various industrial materials is considered. The protective cover is highly required to have, in addition to the cut resistance, a function of matching the shape of the cover with a shape of the material as accurately as possible. In order to produce a protective cover which meets such needs, the protective cover may be produced as a woven/knitted textile formed in a shape corresponding to the shape of the material. However, in this case, a problem arises that, when the shape of the material is complicated, the shapes cannot be completely matched with each other, and the woven/knitted textile for covering may be partially loosened. In order to solve the problem, a manner may be considered in which a woven/knitted textile is produced by using yarns having a high thermal shrinkage rate, and a heat treatment is then performed to develop the high shrinkage, thereby obtaining a protective cover that has a corresponding shape. However, a melting point for a polyethylene fiber is lower than that for another resin, and a temperature at which the thermal shrinkage is caused to occur needs to be as low (70° C. to 100° C.) as possible. Therefore, it is preferable that a shrinkage stress and a shrinkage rate at 70° C. to 100° C. are relatively high. However, a polyethylene fiber that has a low shrinkage stress and a low shrinkage rate at about 20° C. to 40° C., and simultaneously has a high shrinkage stress and a high shrinkage rate at 70° C. to 100° C., cannot be obtained in a conventional manner, and selection needs to be made depending on applications (see Patent Literature 1, 2, 3, and 4).
Thus, a highly functional fiber that satisfies a required shrinkage rate in a predetermined temperature range, and has an excellent cut-resistance, and a protective woven/knitted textile formed thereof have yet to be completed.